This application relates generally to photography and, more specifically, to diffusion transfer photographic systems including products and processes.
Diffusion transfer photographic systems wherein images are formed in color by the use of image dye-providing materials such as dye developers are well known in the art. Generally, multicolor transfer images are formed by processing an exposed multicolor photosensitive silver halide element with an aqueous alkaline processing composition distributed between two sheet-like elements, one of these elements including an image receiving layer. The processing composition is so applied and confined within and between the two sheet-like elements as not to contact or wet outer surfaces of the two superposed elements, thus providing a film unit whose external surfaces are dry. The processing composition preferably is distributed in viscous form from a pressure rupturable container.
It is known in the art to carry out development in the presence of development restrainers whereby development of exposed silver halide is continued for a period of time sufficient to form an imagewise distribution of diffusible unoxidized dye developers in undeveloped areas of the silver halide emulsion layer(s) with the unoxidized dye developers being transferred by diffusion to a superposed image receiving element and, after the predetermined development period, restraining further development of exposed silver halide by means of the development restrainer. See, for example, U.S. Pat. No. 3,265,498. Various development restrainers which are useful for such purposes are known including mercaptoazoles such as 1-phenyl-5-mercaptotetrazole. However, the use of such development restrainers is subject to certain limitations. For example, U.S. Pat. No. 3,260,597 discloses that mercaptoazole development restrainers or "arrestors", such as 1-phenyl-5-mercaptotetrazole, can not be used in the aqueous alkaline processing compositon in any appreciable amount because development of exposed silver halide will be stopped prematurely particularly in the outer blue and green sensitive emulsion layers of a multicolor system.
It is also known in the art to use blocked development restrainers which are designed to provide a timed release of a development restrainer during the development process. See, for example, U.S. Pat. No. 3,698,898 which discloses the use of quinone- or naphthoquinone-methide precursors which release a photographic reagent such as 1-phenyl-5-mercaptotetrazole in the presence of alkali; U.S. Pat. No. 4,009,029 which discloses a class of cyanoethyl-containing blocked development restrainers; German Offenlegungsschrift No. 2,427,183 which discloses various blocked development restrainers, and U.S. Pat. Nos. 3,260,597 and 3,265,498, referred to above, which disclose hydrolyzable blocked restrainers.
The use of phenylmercaptetrazole compounds which are substituted on the phenyl ring as development inhibitors in certain conventional photographic systems is also known. See, for example, Research Disclosure, July 1974, page 12, and U.S. Pat. No. 3,295,976.